Manufacturing process of galvanized steel sheet
Release time:
2023-02-09
The hot-dip galvanizing process is divided into flux method and protective gas reduction method according to the pretreatment method. The latter is divided into old law and new law - Sendzimir law and improved Sendzimir law.
Hot dip galvanizing process
The hot-dip galvanizing process is divided into flux method and protective gas reduction method according to the pretreatment method. The latter is divided into old law and new law - Sendzimir law and improved Sendzimir law.
Flux method
It is to pickle the annealed steel plate to remove the oxides on its surface, then carry out chemical treatment through a flux tank containing ZnCl2 and NH4Cl, and then enter the molten zinc pot for galvanizing. The strip steel coming out of the zinc pot is drawn upright and wiped by an air knife to control the thickness of the coating.
protective gas reduction
It is the most common and widely used process for continuous hot-dip galvanizing of modern strip steel, and the typical one is the Sendzimir method. The characteristic is that continuous annealing and galvanizing are connected on one production line, and operations such as pickling and flux treatment in the flux method are canceled. The strip steel advanced oxidation furnace burns the residual emulsion on the surface and forms a blue oxide film, then the strip steel enters the reduction furnace for recrystallization annealing, and the surface oxide film is reduced by hydrogen to sponge iron; finally the strip steel is cooled in a protective atmosphere Enter the zinc pot for galvanizing at a temperature slightly higher than that of the zinc liquid.
Modified Sendzimir
It is developed and improved from the old method. The core of this method is that the strip steel is first heated without oxidation to remove surface grease, dust and moisture, and then enters the reduction furnace filled with a protective gas containing 15% to 30% of hydrogen and 85% to 70% of nitrogen to complete normalization or Recrystallization anneals and reduces the iron oxide on the surface. Improved Sendzimir galvanizing process. The oxidation and reduction of the old method are carried out separately, but the new method connects the non-oxidizing rapid heating furnace with the reduction furnace, and the strip steel hardly oxidizes when passing through the non-oxidizing heating furnace. Compared with the old method, the new method can increase the output of the unit; reduce the concentration of hydrogen in the protective atmosphere, thereby reducing the cost and the risk of hydrogen explosion; the waste protective gas discharged from the reduction furnace can be burned in the non-oxidation heating furnace to save part of the fuel; The sealing roller component in front of the reduction furnace is omitted.
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